1. Field of the Invention
This invention relates generally to circuit breakers and, more particularly, to circuit breakers of the electromagnetic type including an operating mechanism and an operating handle.
2. Background Information
Circuit breakers of the electromagnetic type are shown, for example, in U.S. Pat. Nos. 3,329,913; and 4,151,386.
Such electromagnetic circuit breakers typically comprise an operating mechanism including a movable contact, which is mounted on a movable arm, and a fixed or stationary contact. An operating handle is coupled to the movable arm via a linkage mechanism, part of which comprises a collapsible toggle assembly. The movable and stationary contacts are operated between contacts xe2x80x9copenxe2x80x9d and contacts xe2x80x9cclosedxe2x80x9d positions by pivoting the operating handle. The circuit breaker further comprises an electromagnetic device which, in response to one or more predetermined electrical conditions, collapses the toggle assembly to a broken state, in order to electrically trip xe2x80x9copenxe2x80x9d the separable movable and stationary contacts.
During on and off operation, the operating mechanism employs a rigid linkage mechanism, including first and second links, to the operating handle. The first end of the second link is pivotally mounted to the second end of the first link and the second end of the second link is pivotally mounted to the movable arm. This provides an early (i.e., relative to handle throw) toggle-on point. At the point where the operating mechanism toggles and the unbroken linkage mechanism begins to move, there is very little energy stored in the operating mechanism springs. As a result, the circuit breaker can be xe2x80x9cteasedxe2x80x9d on, which causes undesirable and potentially damaging arcing to the separable contacts.
xe2x80x9cSlow makexe2x80x9d is defined as the closing velocity of the circuit breaker separable contacts being directly dependent upon the closing speed of the operating handle. For a circuit breaker operating at relatively high voltages (e.g., 480 to 600 VAC), this results in a greater tendency for the separable contacts to weld closed, and significantly reduces the number of switching operations in the operating life of the circuit breaker.
It is believed that circuit breakers including a direct linkage mechanism or links connecting the operating handle to the movable contact arm are inherently xe2x80x9cslow makexe2x80x9d and xe2x80x9cslow breakxe2x80x9d.
U.S. patent application Ser. No. 10/185,858, filed Jun. 27, 2002, discloses a circuit breaker including a pivot lever having a first arm with a first end adapted for engagement with a movable contact arm, and a second arm having a second end adapted for engagement with an operating handle assembly. The first end of the pivot lever carries a U-shaped hook member pivotally disposed thereon. The hook member has a J-shaped hook, which is adapted for engagement with the movable contact arm, and a J-shaped pivot end, which is pivotally mounted in an opening of the first arm. In order to eliminate the dependency between the movable contact arm and the operating handle assembly, the J-shaped hook initially hooks the movable contact arm. The pivot end of the hook member is inserted into the first or free end of the pivot lever. The pivot lever pivots about a pin and translates the hook member and the movable contact arm movement up to the operating handle assembly. The second or handle end of the pivot lever interacts with a blocking disk of the operating handle assembly, which disk rotates about the same center as the operating handle, but is allowed independent movement.
It is known to provide xe2x80x9cfast breakxe2x80x9d and xe2x80x9cfast makexe2x80x9d operation in circuit breakers, such as, for example, miniature circuit breakers.
There is room for improvement in circuit breakers.
These needs and others are met by the present invention, which provides a snap lever for a linkage mechanism of a circuit breaker operating mechanism. The snap lever holds an operating mechanism linkage in the open position of the operating mechanism and releases the linkage as the circuit breaker operating handle moves from the open position toward the closed position of the operating mechanism, in order to snap close the separable contacts.
In accordance with an aspect of the invention, a circuit breaker comprises: a case; separable contacts including a fixed contact and a movable contact; and an operating mechanism for opening and closing the separable contacts, the operating mechanism including a closed position, an open position, an operating handle for moving the operating mechanism between the open and closed positions, a movable contact arm carrying the movable contact, a linkage having a first end and a second end, and a snap lever, the second end of the linkage being pivotally mounted to the movable contact arm, the snap lever holding the linkage in the open position of the operating mechanism and releasing the linkage as the operating handle moves from the open position toward the closed position of the operating mechanism, in order to snap close the separable contacts.
The case may have an opening, the linkage may further have a pivot, and the operating handle may include a first portion extending through the opening of the case, a second portion within the case, and at least one extension spring extending between the second portion and the pivot.
The linkage may further have a first link and a second link, the first link having a first end and a second end, the first link being pivotally mounted to the pivot at the first end of the first link, the second link having a first end and a second end, the second link being pivotally mounted to the second end of the first link at the first end of the second link and being pivotally mounted to the movable contact arm at the second end of the second link.
The case may house a frame, the frame may include a pin, and the snap lever may pivot on the pin. The snap lever may include a first end and a second end, the first end of the snap lever resting against the frame, in order to provide a spring force to return the snap lever to hold the linkage in the open position of the operating mechanism.
The second end of the snap lever may include a cup, and the linkage may further have a detent which is captured by the cup.
The operating handle may include a first surface, the snap lever may include a second surface holding the linkage in the open position of the operating mechanism and a third surface, and the operating mechanism may further include a snap closed position between the open position and the closed position, with the first surface of the operating handle engaging the third surface of the snap lever at the snap closed position of the operating mechanism, in order that the second surface of the snap lever releases the linkage as the operating handle moves from the open position toward the closed position of the operating mechanism.
The case may have an opening, the linkage may further have a pivot, and the operating handle may include a handle extending through the opening of the case, at least one arm having the first surface within the case, and at least one extension spring extending between the at least one arm and the pivot, with the first surface of the at least one arm engaging the third surface of the snap lever, in order to release the linkage and allow the at least one extension spring to move the operating mechanism to the closed position.